The present invention is directed to an improved spindle assembly for a single or a multiple spindle machine. Multiple spindle machines are well known in the art. The machine shown in the drawings is a modified Acme-Gridley multiple spindle machine. Other types of multiple spindle machines are shown in, for examples, U.S. Pat. Nos. 3,688,364; 3,744,355; 3,978,565; and 4,011,777.
In many prior art multiple spindle machines, a workpiece holding collet is positioned at the end of each spindle. The collet is movable between an open and closed position. When in the closed position, it holds a workpiece while an exterior machining operation is performed. These machining operations may include cutting operations, drilling operations, tapping, broaching, deburring, or any other similar type machine operations. In many prior art machines, when the exterior machining operation was completed, the prior art spindles included mechanical ejector mechanisms within the spindles which contacted the back of the workpiece to eject the workpiece from the spindle. A prior art mechanical ejector is disclosed in U.S. Pat. No. 4,106,376. This patent discloses the use of an ejector rod to eject the workpiece. This patent also discloses the use of an air blast to blow air into the rear end of the spindle assembly to blow chips and coolant out of the collet and to discharge the workpiece.
In using several of the prior art spindle assemblies, there is often no consistency with respect to the location of the front end of the collet after the workpiece has been removed and a new workpiece is inserted. Often, the axial relationship of the collet relative to the front end of the spindle assembly and to the exterior tool must constantly be monitored and adjusted.
The primary object of the present invention is to provide an improved spindle assembly for a multiple spindle machine in which a liquid, such as a water base liquid or an oil base liquid, is utilized to discharge the workpiece from the collet.
In one embodiment of the present invention, an inner shaft which is positioned within the outer tubular member of the improved spindle assembly includes a tool holder mounted adjacent its outer end so that an interior machining operation may be performed on the back side of the workpiece at the same time as the exterior machining operation is being performed on the front side of the workpiece.
In still another embodiment of the present invention, the front end of the collet, which holds the workpiece is axially fixed relative to the outer end of the spindle assembly. The collet can be opened and closed to release and position a new workpiece while maintaining the correct position of the collet and workpiece relative to the tool thereby eliminating many of the adjustments needed in prior art spindle assemblies.